Vestibular migraine (VM), also known as migrainous vertigo and migraine-associated vertigo, affects about 1% of the general population and 10% of patients seen in dizziness clinics, yet relatively little is known about its clinical course or the functional impairment that it causes. There is no proven therapy. Various medications have been used clinically to treat VM, but no rigorous research data support these practices. Triptans are a class of medications that are very effective for aborting migraine headaches. Case reports suggest that triptans might also be effective for treating vertigo attacks in patients with VM. One controlled study was attempted and suggested benefit, but too few subjects were enrolled to reach statistical significance. We propose a two-center, randomized, placebo-controlled, parallel group trial of rizatriptan to assess its efficacy and tolerability for treating vestibular attacks n patients with VM. Our primary Specific Aim is to test the hypotheses that rizatriptan will be superior to placebo (1) for reducing the severity and duration of vestibular attacks in patients with VM, (2) for reducing other symptoms associated with VM, (3) for improving treatment satisfaction and health-related quality of life (HRQOL) in patients with VM, and (4) that rizatriptan will be well tolerated by patients with VM. Our secondary Specific Aim is to collect data on the clinical course of VM and its common comorbid conditions to plan future Phase III trials of rizatriptan and other medications for treating VM. This study will begin with an observation period lasting up to 6 months during which the severity and frequency of vestibular attacks will be measured. Co-existing conditions that might confound rizatriptan therapy will be assessed and stabilized. Patients who have two moderately severe vestibular attacks during the observation period will immediately be randomized to treat three subsequent attacks with either rizatriptan or placebo in a ratio of 2:1. Medication response and adverse effects will be measured after each treated attack. Additional data will be collected at regular intervals to evaluate the severity of associated symptoms and changes in treatment satisfaction and HRQOL. If successful, this study will provide the first data for an evidence-based treatment of VM and set the stage for larger Phase III trials.